Hebei Messi Biology Co., Ltd. stated that nano-magnesium oxide prepared by chemical method has excellent properties such as high purity, small particle size, large specific surface area, high hardness, high reaction activity, strong adsorption and good low-temperature sintering, and can be used as an adsorbent for environmental pollution control.
This study conducted a systematic study on the preparation of nano magnesium oxide powder and magnesium oxide-based adsorbents, and applied them to the simultaneous desulfurization and denitrification test of flue gas. On this basis, the best method for regeneration of nano-magnesium oxide adsorbents was obtained through comparison of various regeneration methods, and good treatment effects were obtained. At the same time, the adsorption mechanism of nano-magnesium oxide adsorbents for simultaneous desulfurization and denitrification was studied and analyzed. The properties, uses and preparation methods of nano-magnesium oxide were reviewed, and the preparation methods of its powder and adsorbent were studied in depth.
The two methods of direct precipitation method and microwave water bath heating method and uniform precipitation method and microwave water bath heating method were experimentally compared. The results showed that nano-magnesium oxide powder with good crystallization and large specific surface area was prepared by combining MgSO4·7H2O and Na2CO3 as raw materials, adding surfactant polyethylene glycol 1000, and adopting a direct precipitation method and a microwave water bath heating method. The effects of the reaction temperature and time of the precursor, the calcination temperature and time, and the amount of high molecular weight polyethylene glycol on the specific surface area of the powder were studied. The structure and morphology of nano-magnesium oxide powder and the thermal decomposition temperature of its precursor were analyzed by thermogravimetric analyzer (TGA), X-ray diffractometer (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), etc.
The results showed that the nano-magnesium oxide powder precursor was calcined at 500℃ for 1.5h, and the specific surface area reached a maximum of 183.35m2/g, and the average particle size was 7.2nm. The nano-magnesium oxide-based adsorbent was prepared by blending method (nano-magnesium oxide powder: MgSO4·7H2O: sweet powder = 75:32:1, mass ratio). In the flue gas desulfurization and denitrification device designed and installed by ourselves, the simultaneous desulfurization and denitrification performance of nano-magnesium oxide-based adsorbent was investigated, the influence of various factors on the removal efficiency was explored, and the state of the adsorbent before and after simultaneous desulfurization and denitrification was characterized. The results show that when the flue gas temperature is 120℃-180℃, the bed height is 5cm, the air velocity in the adsorption tower is less than 3400 h-1, the flue gas is in aerobic conditions, the SO2 concentration is 2000mg/m3, and the NO concentration is 500mg/m3, the desulfurization efficiency can be maintained at about 98.03% within 60 minutes of adsorption, and the denitrification efficiency can be maintained at about 85.74%. The adsorbent has good stability.
In the regeneration experiment, thermal regeneration, steam regeneration and alkali washing were studied. By comparing the effects of simultaneous desulfurization and denitrification of the regenerated adsorbent, it was shown that the alkali regeneration method had the best regeneration effect. Further experiments showed that the regeneration effect was best when 5.37g of nano-magnesium oxide-based adsorbent was soaked in 0.25 mol/L, 100ml sodium hydroxide at 20°C for 30 minutes. The simultaneous desulfurization and denitrification efficiency of the adsorbent after alkali washing and regeneration was improved. The stability of the simultaneous desulfurization and denitrification of the adsorbent after regeneration was good, and the nano-magnesium oxide-based adsorbent could be regenerated repeatedly. The self-designed and installed simultaneous desulfurization and denitrification adsorption-regeneration integrated pneumatic fluidized circulation treatment regeneration device was used for the test. After 60 minutes of continuous test, the removal efficiency of SO2 remained at 100%, and the removal efficiency of NOx remained above 74.3%.
Finally, the mechanism of simultaneous desulfurization and denitrification of nano-magnesium oxide-based adsorbent was studied. The nano-magnesium oxide-based adsorbent was characterized and analyzed by BET, SEM, XRD, FT-IR, etc. before and after simultaneous desulfurization and denitrification and before and after regeneration. The simultaneous desulfurization and denitrification of nano-magnesium oxide-based adsorbent is a combination of physical adsorption and chemical adsorption, among which chemical adsorption is the main one. A series of complex chemical reactions occurred when 8O2 and NOx came into contact with the adsorbent. After washing with alkaline solution, alkaline groups were added to the surface of the adsorbent, which was helpful for the removal of SO2 and NO, and it was speculated that the adsorbent had a catalytic oxidation effect on NO at this time, and the catalytic effect further improved the desulfurization and denitrification efficiency. The experiment showed that the magnesium oxide-based adsorbent can be regenerated repeatedly, and the improved simultaneous desulfurization and denitrification adsorption-regeneration integrated system can be applied in actual production.